A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateTrusted ADU Builders for San Jose Homeowners
Adding an accessory dwelling unit in San Jose means dealing with setbacks, zoning letters, and a permit process that stalls projects for months when the paperwork is wrong. For homeowners in neighboring areas, we also work with ADU Builders - Santa Clara to handle similar requirements. Reed Calloway started Fielding ADU San Jose inside the Garrison Partners family, which has been building to The Garrison Standard since 2006, to fix exactly that. We put the price in writing before the first nail goes in, we pull permits by the book, and we back every build with a 365-day written guarantee. If you’re weighing a detached unit, a garage conversion, or a JADU, call (669) 201-3984 and we’ll walk you through the real cost for your lot.
ADU Construction
ADU Construction covers the full build from the foundation or existing slab up through framing, mechanical, and finish work, including site preparation, utility connections, and final inspection. Homeowners in San Jose use it for a complete accessory unit in the backyard, above a detached garage, or attached to the side of the primary house. Our crews handle conventional construction using James Hardie siding as well as panelized prefab systems. A stick-built ADU in San Jose typically runs $350 – $550 per square foot, which puts a 500-square-foot one-bedroom unit between $175,000 and $275,000 before permit and utility connection fees. The written price you approve on day one is the number on your final invoice.
Foundation and Site Work
A level pad, correct drainage, and proper setbacks make or break the build. We verify your council district’s setback rules and handle the grading, excavation, footing, and any retaining issues before framing starts.
Mechanical and Utility Runs
San Jose requires separate water, sewer, and electric service for detached units, which means trenching from the main or the property line. We handle the trench, the panel, the sewer lateral, and the inspection sign-off.
Detached ADU
A Detached ADU is a standalone living unit built in the rear or side yard, fully separated from the primary residence, with its own entrance, kitchen, bath, and address. San Jose homeowners choose this when they want to rent the unit out for income, house an aging parent, or keep a private space for adult children. We build detached units using conventional framing with James Hardie siding or faster panelized platforms like Abodu and Plant Prefab. Expect a detached ADU in San Jose to run $190,000 – $320,000 for a 400 – 600-square-foot one-bedroom, depending on site access, utility distance, and foundation conditions. Every price goes in writing before work starts.
Setback and Height Limits
San Jose allows a detached unit to be 16 feet tall, up from 14 feet in earlier code cycles, and most residential zones allow a rear setback of 4 feet. We check your lot’s specific zoning designation before design, because an R-1 lot in Willow Glen and an R-2 lot near Alum Rock can have different rules.
Rental and Resale Considerations
A permitted detached unit with its own meter and address adds more appraisal value than an unpermitted conversion ever will. We build to the current California Energy Code so your unit rents legally and sells cleanly.
JADU
A JADU, or junior accessory dwelling unit, is a living space of up to 500 square feet created entirely within the walls of an existing single-family home, often from a spare bedroom, attached garage, or utility room. San Jose homeowners use a JADU when they want a separate rental unit or a private suite for a relative without the cost of a new foundation. The city allows one JADU per single-family lot, and it must include a small kitchen and either a private bath or shared bath access. A JADU conversion in San Jose typically runs $80,000 – $160,000 depending on whether you’re converting finished interior space or an unfinished attached garage that needs drywall, insulation, and floor work. We provide the written price before any demolition starts.
JADU vs. Full ADU
A JADU almost always costs less than a detached unit because there’s no new foundation, no separate utility drop, and no trenching across the yard. The tradeoff is square footage and a shared lot, which matters if you’re planning to rent both units separately.
Owner-Occupancy Rules
San Jose requires the owner to live on the property, either in the main house or the JADU, through the life of the unit. We walk you through what that means before you commit, so there’s no surprise two years into a rental lease.
ADU Plans
ADU Plans are the architectural drawings, site plan, energy calculations, and structural details that the City of San Jose requires before a building permit can be issued. We produce plans that meet current California building code and San Jose’s specific detached dwelling standards, then submit them under our permit application. Plan sets for a straightforward detached ADU in San Jose run $6,000 – $14,000 including site survey, Title 24 energy calculations, and structural engineering. You get a price for the plans separately from the build, both in writing.
Site Survey and Zoning Review
Before drawing a wall, we pull the parcel record from the Santa Clara County assessor’s office and verify lot dimensions, easements, and the specific zoning district. That catches setbacks and coverage limits early, before you pay for revisions.
Prefab-Ready Drawings
If you’re using a panelized system from Abodu or Plant Prefab, the manufacturer has approved architectural sets that speed local review. We integrate those sets with your site-specific foundation and utility plans so the permit application moves without a design conflict.
ADU Contractor
An ADU Contractor is the licensed general contractor who pulls the building permit, schedules inspections, manages subcontractors, and carries responsibility for the entire build from staking the footprint to the final sign-off. San Jose homeowners call us after a previous contractor went silent or left a permit board with empty spaces. Our crews are background-checked and uniformed, and a live person answers the phone 24 hours a day, 7 days a week. General contractor fees in San Jose for an ADU project typically run 10 – 20% of the total build cost, and that percentage is included in the written price you approve before work starts, not added later.
Permit Pulling and Inspections
We pull all required permits from the City of San Jose building division and schedule every inspection, including foundation, framing, rough mechanical, and final occupancy. You never chase an inspector, and you never wonder whether the work is permitted.
Subcontractor Oversight
Electrical, plumbing, and roofing subs are only useful if someone is watching the details. Reed Calloway manages every trade on the schedule and checks their work against the approved plan before any inspection is called.
ADU Design
ADU Design is the process of choosing the floor plan, exterior materials, window placement, and interior finishes for your unit, and it happens before any permit drawings get submitted. San Jose homeowners use design to decide between a 400-square-foot studio and a 600-square-foot one-bedroom, and to set the rental rate or the resale appeal of the property. Design fees are included in the plan set price, so you’re not paying separately for a designer’s time. We work with the Abodu and Plant Prefab design libraries when that fits your lot, and we draw custom layouts when it doesn’t.
Matching the Main House
A unit that looks like it was always there rents faster and appraises higher. We match roofing material, exterior siding like James Hardie lap, and trim style to the primary residence so the property reads as one place, not two.
Lot Coverage and Orientation
Windows aimed at the neighbor’s side yard are a mistake, and so is a unit that eats the only usable outdoor space. We orient the floor plan around your actual lot, not a generic catalog image, and show you where the unit will sit before you sign.
Backyard ADU
A Backyard ADU is a detached accessory dwelling unit placed in the rear yard of a single-family property, usually behind the primary house and accessed by a side path or the existing driveway. If you’re looking just north of the city, our ADU Builders in Sunnyvale handle backyard units with the same approach. San Jose homeowners build backyard units when the main house is at the front of a deep lot and the rear yard is underused grass or storage. We build backyard units conventionally with James Hardie siding or as panelized structures from Plant Prefab and Abodu, depending on access and elevation. A backyard ADU in San Jose typically runs $200,000 – $340,000 for a 500 – 700-square-foot one-bedroom or two-bedroom unit, with the biggest variables being utility distance, site access for equipment, and any retaining wall work.
Site Access for Equipment
Lots in neighborhoods like Willow Glen and East San Jose often have narrow side yards that limit crane and concrete pump access. We assess the equipment path during the estimate and price the build to match, so the number doesn’t move when the concrete truck shows up.
Rear Yard Setbacks
San Jose requires a minimum 4-foot rear and side setback for detached ADUs, but some lots carry recorded easements that change that number. We pull the recorded map during planning and design around every easement, not just the standard rules.
Brands We Service
We build with Abodu and Plant Prefab panelized systems, and we use Tuff Shed structures as a permitted starting point for detached studios when the lot and budget call for it. Plant Prefab units arrive as factory-built panels that assemble on site faster than stick framing, and we handle the foundation, utility connections, and finish package around them. With Abodu, we coordinate the foundation and site work to their exact specifications, so the factory-floor precision isn’t lost on a sloppy pad.
For conventional construction, we side units in James Hardie fiber cement because it holds up to San Jose’s dry summers and wet winters without the warping you get from wood plank. Whether you have a specific prefab spec sheet or no idea which system fits, we can help. Call (669) 201-3984 and we’ll give you a straight answer on what works for your lot and budget.
Signs You Need a Pro Right Now
- Your permit application has been rejected twice. San Jose’s planning department sends back plans for missing energy calculations, wrong setback callouts, or incomplete site surveys. A rejection letter doesn’t mean the project is dead, but it does mean the drawings need professional revision before you burn more months.
- A previous contractor walked off mid-build. If the slab is poured, the framing is half up, or the rough electrical is exposed, your permit clock is still running and the city will eventually want to know who’s finishing the work. An unfinished permitted project can complicate a future sale.
- The price keeps changing. A contractor who can’t hold a number on a foundation quote won’t hold one on fixtures. If you’ve already approved a budget and the invoices keep arriving higher, get a written line-item price from someone who doesn’t work that way.
- Your lot has unusual conditions. Sloped lots in the Santa Cruz Mountains foothills, high water tables in parts of South San Jose, or narrow access in older Willow Glen neighborhoods all change the foundation design. Guesswork here becomes a crack in the slab two years later.
- You’re getting letters from the city. An unpermitted structure or a conversion that didn’t get final sign-off will eventually trigger a code enforcement notice. The fix is almost always to bring it up to current code with an amended permit, and that’s faster done now than after a fine.
Our Process, Step by Step
- 1
Site walk and lot assessment. Reed Calloway or a senior project lead walks the property, measures the lot, checks access, and asks what the unit is for: rental income, family, or resale value. You get a written estimate based on what’s actually on the ground, not a square-footage guess.
- 2
Zoning and feasibility check. We pull the parcel record, verify your zoning district, and check setbacks, height limits, and any HOA or historic district overlays. This is where we find out whether a JADU or a detached unit is the better play for your lot.
- 3
Written price and plan set. We produce drawings, engineering, and energy calculations, and we hand you a fixed price for the build before you sign a construction agreement. That price covers permits, materials, labor, and our contractor fee, with no change orders hiding in the margins.
- 4
Permit submission and build. We submit the plans to the City of San Jose, respond to plan-check comments, pull the permit, and start construction. Background-checked, uniformed crews do the work, and the same project lead you met on day one is the one you call with questions.
- 5
Final inspection and handover. We schedule the final inspection, walk the unit with you, and hand over the written 365-day guarantee. If something fails inside that year, we return and correct it at no charge. That’s the Garrison Standard, and it’s on paper.
How Much Does ADU Builders Cost in San Jose?
A JADU conversion in San Jose runs $80,000 – $160,000 when the space is already within the main house. A detached 500-square-foot unit runs $175,000 – $320,000 depending on site access, foundation type, utility distance, and whether you use conventional framing or a panelized system like Plant Prefab. The biggest cost drivers are the foundation (slab-on-grade costs less than a raised floor over a sloped lot), the utility trench (a unit 80 feet from the sewer lateral costs more than one 20 feet from it), and interior finish choices. To avoid overpaying, get a written line-item price before any work starts and insist that the number you approve is the number on the final invoice. Our free estimate includes a site walk, a zoning feasibility check, and a fixed written price for the full build. Call (669) 201-3984 to schedule yours.
Our Service Area Near San Jose
We build ADUs throughout San Jose and the neighboring Santa Clara County communities, including Sunnyvale, Campbell, Menlo Park, Saratoga, Newark, Scotts Valley, Stanford, Boulder Creek, Alum Rock, Burbank, and Santa Clara. Our home page covers the full range of services, and if you’re weighing a unit in a neighboring city, see our pages for ADU Builders in Sunnyvale and ADU Builders in Campbell. Most San Jose estimates are scheduled within a week of your call.
Serving San Jose, CA - Our Local Coverage Area
We’re based in the San Jose area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked Questions About ADU Builders in San Jose
An San Jose ADU Builders is a licensed general contractor who designs, permits, and constructs accessory dwelling units on residential lots. We handle the entire process from zoning review through final inspection, including plan sets, foundation work, framing, mechanicals, and finishes. No third-party project manager gets dropped into your job halfway through.
A JADU conversion typically takes 3 – 5 months from permit to final inspection, while a detached ADU usually takes 6 – 10 months depending on site conditions and plan-check turnaround. San Jose’s building department currently runs several weeks for initial plan review, and prefab systems can shorten on-site framing time but don’t remove the foundation or utility work. The schedule goes in writing before we start.
Expect $80,000 – $160,000 for a JADU, and $175,000 – $340,000 for a detached unit, with permit fees, utility connections, and site work included in our written price. Plan sets run $6,000 – $14,000 separately. Call (669) 201-3984 for an exact quote on your lot; estimates are free.
Yes. We build foundations, utility connections, and finish packages for Abodu, Plant Prefab, and other panelized systems, and we use Tuff Shed structures as permitted starting points where appropriate. If you’ve already picked a prefab brand, we’ll align the site work with their factory specs. If you haven’t, we’ll tell you which system makes sense for your budget.
We pull all permits from the City of San Jose building division and manage every inspection from foundation through final occupancy. Our plan sets are drawn to current California and San Jose code, including Title 24 energy compliance, and we respond to plan-check comments on your behalf. You don’t stand in line at city hall.
Every ADU we build is covered by the Garrison Standard: a written 365-day guarantee on workmanship defects. If something fails inside that year, we return and correct it at no charge. The guarantee is spelled out on paper before construction begins, including what it covers and how we make it right.
Have a rough idea of the unit’s purpose (rental, family, resale), know your property’s lot dimensions if you have the survey, and be ready to walk the site with us. You don’t need drawings or a design picked out yet. The first visit is a straight conversation about what’s possible on your lot and what it costs.
Schedule Your ADU Builders Service in San Jose Today
You’ve dealt with moved schedules and silent contractors. We work differently. Call (669) 201-3984 to schedule a free site walk and get a written price for your ADU, garage conversion, or room addition in San Jose. Reed Calloway and the Fielding ADU San Jose crew build to The Garrison Standard: show up in the window, price in writing, by the book, leave it clean, stand behind it for a year.
Written by Reed Calloway, Owner at Fielding ADU San Jose, serving San Jose since 2006.
